Grantee Research Project Results
2019 Progress Report: Assessment of Stormwater Harvesting via Managed Aquifer Recharge to Develop New Water Supplies in the Arid West: the Salt Lake Valley Example
EPA Grant Number: R835824Title: Assessment of Stormwater Harvesting via Managed Aquifer Recharge to Develop New Water Supplies in the Arid West: the Salt Lake Valley Example
Investigators: Dupont, R. Ryan , McLean, Joan E , Null, Sarah , Peralta, Richard , Jackson-Smith, Douglas
Institution: Utah State University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2015 through August 31, 2018 (Extended to August 31, 2020)
Project Period Covered by this Report: September 1, 2018 through August 31,2019
Project Amount: $749,998
RFA: Human and Ecological Health Impacts Associated with Water Reuse and Conservation Practices (2014) RFA Text | Recipients Lists
Research Category: Human Health , Water
Objective:
The project is designed to test the hypothesis that Managed Aquifer Recharge (MAR) via Green Infrastructure (GI) systems for stormwater harvesting is a technically feasible, socially and environmentally acceptable, economically viable, and regulatorily achievable option for developing new water supplies for arid Western urban ecosystems experiencing increasing population, and climate change pressures on existing water resources
Progress Summary:
Research Component 1, Monitoring of Existing MAR/GI Stormwater Management Systems–
For the two sites treating primarily pavement runoff (300 East and the Early Childhood Education Building, USU, in Logan), overlapping 95% Confidence Intervals of measured runoff pollutant concentrations during Year 3 showed differences between these sites only for TP and Pb, with statistically higher values observed at the 300 E site. Repeat measurements at the 300 E site in Year 4 indicated that concentrations were consistent over time as did the monitoring of the green roof on the Early Childhood Building on USU Campus during Year 4. These consistent pollutant concentrations suggest runoff values generated from this study are representative of specific land use conditions and roofing materials for which they were measured.
The 300 East bioswale continues to release dissolved solids as indicated by elevated EC values, and continues to be a net producer of low concentrations of dissolved Ni, As, and Pb. However, attenuation of TN, TP, Cr, Cu, Zn, As, and Pb with depth in the soil underneath the 300 East bioretention site was shown by multiple depth lysimeter measurements, suggesting further migration of pollutants from the site is expected to be limited.
Results of the field evaluation of the effect of plant species and loading rate on pollutant removal by bioretention systems at the Green Meadow site verified the impact of plant species on nutrient and metal concentrations in bioretention system pore water and soil. Arsenic solubilization in pore water greater than in the unplanted treatment was evident in most vegetated systems but limited mobility out of the root zone was documented from pore water and groundwater concentrations, and from soil pollutant concentration measurements with depth. Many metals and nutrients are mobilized within the active plant root zone, but groundwater concentrations indicated these pollutants are not mobilized out of this active zone into underlying groundwater. Pollutant loading rate had much less impact on pollutant pore water and soil concentrations than did plant type.
Research Component 2, Integrated Modeling– To support precipitation-runoff modeling, an Artificial Neural Network (ANN) based methodology was developed for imputing missing weather data values. By achieving approximately 26% of the root mean square error of a standard imputation method, the ANN-based technique provided over 300% improvement in accuracy of imputing net radiation. Interestingly, the ANN-based method did not offer a significant advantage over standard methods for estimating daily average temperature and daily precipitation, however. Simulations reaffirmed that most Red Butte Creek streamflow is hyporheic and comes from groundwater. In Water Years 2016 and 2017, 95% of RBC streamflow just above the Red Butte Reservoir is derived from groundwater, and approximately 5% of streamflow is direct runoff.
Differences in seepage estimates between the surface water model (QUAL2KW) of Red Butte creek and the MODFLOW HypoRBC groundwater model is inevitable when utilizing the short time calibrated surface water model. However, the maximum difference between model predictions for seepage flow rates for the April and June 2016 data sets was 0.31 and 0.225 cfs, respectively, which are considered reasonable and acceptable. Furthermore, the HypoRBC groundwater model shows a maximum discrepancy from the calibrated Qual2kw seepage flow rate and cumulative seepage volume for these simulation periods of only 2.53%.
To illustrate the practical application of WinSLAMM to model stormwater runoff and infiltration for secondary recovery, a case study in the Salt Lake Valley near the Jordan River was carried out to evaluate the potential for Spring runoff infiltration through shallow groundwater recharge coupled with Summer groundwater recovery for turf grass irrigation under Northern Utah climatic conditions (historical April, May, early June rainfall patterns). Results indicated a stormwater recovery effectiveness from 10.7% to 52.7% depending on irrigation scheduling, and a feasible constant recovery rate of shallow groundwater from 1.0 to 10.6 gpm. At these recovery rates, from 1 to 10% of the small landscape area of the modeled development could be irrigated with this harvested stormwater.
Research Component 3, Social Science Research– Results from the household surveys demonstrated that individual residents are largely unaware of how stormwater is handled in their neighborhoods. In cases where GI has been deployed, subsurface storage/infiltration was well regarded, while surface storage/infiltration systems had a more uneven track record (mainly because of poor design, implementation or maintenance). The December 2018 SAB participants indicated that the combined modeling effort undertaken in the project seemed too large for small developments but a city could use it for retrofit projects to get “credit” for their pollutant load reductions, and developers may be encouraged to use it for identifying optimal GI approaches for their developments.
Future Activities:
All laboratory analysis of samples collected from the Green Meadows field demonstration site and all GI systems have been completed. Data reduction will continue to allow comparison of the performance of GI/MAR systems as a function of vegetation type and pollutant loading. In addition, disaggregation of pollutant loading data from all of the field sites will continue in order to explore relationships between pollutant concentrations and storm intensity and duration using rainfall data available from each of the field sites. If pollutant load versus storm return period relationships can be developed, further improvements can be made to rainfall runoff inputs to the integrated modeling effort.
On-going work in the surface and groundwater systems modeling component includes: completing a support-vector machine revision to precipitation and runoff prediction for Years 2051-2060 of climate variability scenarios for Red Butte Watershed; revising previously developed software to link QUAL2KW v. 6 with MODFLOW-SFR for unsteady flow simulations; developing background conditions for the Salt Lake Valley groundwater model and HypoRBC subsystem model including selecting boundary conditions such as time series of groundwater and surface waters flowing out of Red Butte (RB) Canyon at the exit from the RB Reservoir; completion of software and simplified user interface that evaluates sites for injecting stormwater into shallow aquifers with subsequent recovery as secondary water for irrigation (site scale groundwater recharge and recovery); and completion of software that links RB Creek and Jordan River surface water flow models with Salt Lake Valley groundwater flow models to predict basin scale impacts of green infrastructure (GI) implementation on streamflow, groundwater availability and groundwater quality impacts.
When model calibration is complete, surface water quantity and quality changes from stormwater management alternatives will be estimated using the calibrated QUAL2Kw model. Green infrastructure alternatives have been modeled with WinSLAMM at Connor Road as discussed in Fernandez-Valesquez (2018). Each GI alternative provides changes in runoff and nutrient loading (i.e., TP, TDP) for 55 different rainfall events and three green infrastructure types: green roofs/gardens, bioretention cells installed in parking lots, and grass swales implemented on along streets (Fernandez-Valesquez 2018). Three levels of implementation of possible GI, 10%, 50% and 100%, consistent with the approach of Fernandez-Valesquez (2018), will be simulated in the upper Red Butte Creek area. The green infrastructure implementation
results will then be upscaled to a watershed-scale by adding additional implementation areas in the QUAL2Kw and MODFLOW models, and applying WinSLAMM to the much larger (25 square mile), much more diverse land use area in the Salt Lake watershed and central valley discharging to the Jordan River. The Red Butte Creek QUAL2Kw model will connect to an existing Utah DEQ QUAL2Kw model of the Jordan River for a larger-scale analysis of the required level of GI project implementation that must occur to increase summer baseflows, attenuate floods, maintain stream temperatures and dissolved oxygen at tolerable levels for native biota, and significantly reduce total pollutant loads to Red Butte Creek and the Jordan River.
A large workshop/meeting will be organized for May 2020 with stormwater management professionals in Utah including the SAB, additional municipal stormwater managers, engineers, and developers who would be the anticipated audience/users for the integrated modeling tools. The goal of the meeting is to provide highlights of Objective 1 results (field monitoring of GI), provide a demonstration of the final coupled modeling tool and its application to the Red Butte Creek and Salt Lake Valley landscape, to simulate the implications of various configurations and levels of GI implementation across the landscape for water flows and ecosystem service enhancements, and to solicit feedback about how the tool could be useful for decision-makers in other Utah landscape contexts.
In July 2020 two on-line Post-Study evaluation surveys are proposed. Survey 1 is planned to be an on-line survey of the SAB to solicit quantitative and qualitative feedback on the project overall (satisfaction with involvement as project advisors; examples of best outcomes, areas for improvement, etc.). Survey 2 is planned to be an on-line survey of the Utah MS4 municipal stormwater manager community, and will include highlights of project findings, illustrations of project simulations, and questions that will focus on updating perceptions of SW managers about the relative feasibility and impacts of different types of SW-GI in their municipalities (compared to Spring 2018 survey results, and to solicit evaluation feedback about the value, utility, and potential applications of the project modeling tool.
Journal Articles:
No journal articles submitted with this report: View all 22 publications for this projectSupplemental Keywords:
vulnerability, TDS, habitat, indicators, sustainable development, public policy, cost-benefit, engineering, social science, ecology, hydrology, environmental chemistry, Great Basin, agriculture, industry, commercial, residential, stormwater, aquifer recharge, groundwater, green infrastructure, ecosystem services, modelingProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.